<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        function add(a,b){
            return a+b;
           }
        console.log(add(3,4));
    </script>
<!-- _____________________________________________________ -->
    <!-- 在函数表达式存储在变量后，变量也可作为一个函数使用： -->
    <script>
        var x = function add(a,b){
            return a+b;
        }
        console.log(x(3,3)*2);
    </script>
</body>
</html>